and crops grown here supply half of the winter vegetables sold in the united states. but the cost to the environment has been astonishing. because of overdevelopment, the flow of freshwater has dramatically decreased, and excess nutrients from farms and ranches have changed the ecosystem to the point where the region is said to be on the verge of biological collapse. so, what we would like to do is understand the needs of the natural ecosystem as well as the needs of humans as welas the needs of agriculture so that we don't pass that tipping point and have to spend $8 billion restoring the suwannee river basin like we're having to do in the everglades. narrator: to predict the future of the suwannee river basin, scientists first have to understand how it is presently functioning. dr. john martin is a colleague of professor graham's at the universy of florida water institute. his team studieshe healthof t, sampling and testing its water for signs of pollution. because of sandy soils and the soluble limestone-bedrock geology in this part of florida, rivers here run abov